Chert and Flint
Chert is a hard, fine-grained, sedimentary rock with a dark, glassy appearance. It is a form of quartz that occurs within limestone sediment, found in nature after the softer limestone around it wears away. Flint is a variety of chert that occurs as nodules in chalk and marly limestone, commonly considered to be a higher quality chert. Flint produces very sharp edges when broken; it was used by early humans to make hunting tools. Flint gives sparks when struck with steel; it is used in modern lighters to ignite fuel.
Around limestone rocks in western Jordan. The Central Desert pavement is tightly packed with chert and flint.